I hand an Emerson st75u thermostat. Hear is an old 2 wire boiler. Cooling is a newer Unico unit with 3 wires for cooling with separate fan. They are in different locations. I want to control both with the Emerson st75u stat. Emerson makes a c wire workaround unit part number SA-11. I could also pull a c wire from the air conditioner or use an external 24v transformer to power the WiFi in the Emerson stat. I just need a little help with the wiring diagram. Thanks for your time and help.